Oscillatory hydromagnetic flow through a porous medium with variable permeability in the presence of free convection and mass transfer flow

Unsteady two dimensional free-convection and mass-transfer flow of a viscous, incompressible, and electrically conducting fluid through a porous medium with variable permeability in the presence of a transverse magnetic field is studied. The permeability of the porous medium fluctuates in time about a constant mean. The free-stream velocity of the fluid vibrates about a mean constant value and the surface absorbs the fluid with constant velocity. Analytical expressions for the velocity and the skin friction amplitude and phase are obtained. The influence on various parameters entering into the problem is discussed. Numerical results are presented graphically. (C) 2002 Elsevier Science Ltd.